In my version of the perfect RPG, XP would be for "objectives" only. So it wouldn't matter how my character got the job done as long he/she got it done. Bloodbath, bribery, smooth talking, double crossing, whatever. I believe Alpha Protocol used this system. Along with its dialogue mechanic, the XP model was one of the most under rated things about the game. Shame really, Alpha Protocol was a flawed gem. A clunky mess of a game but an excellent role playing experience nonetheless.